1. Field of the Invention
This invention relates generally to hand trucks and the like, and is more particularly concerned with a hand truck having a powered stair-climbing track, and a powered lift apparatus.
2. Background Information
Hand trucks are very well known in the art, and are frequently used as portable means for carrying cargo or freight of almost any type, as long as the item carried is not so large as to overburden the hand truck. The conventional hand truck is of course very effective when carrying objects along generally flat terrain; but, when heavy material must be carried up or down steps, the hand truck offers little assistance.
In package delivery businesses, for example, it is common to provide a hand truck on a delivery van or light truck. Packages that are somewhat too large or heavy to be conveniently carried from the vehicle to the point of delivery can then be manually unloaded from the delivery vehicle and carried to the point of delivery on the hand truck. Many deliverable items are too large and heavy to be manually unloaded by a single operator, but are nonetheless too small to require the use of heavy duty delivery equipment such as a forklift truck. These items are often handled by sending an assistant along with the driver/delivery operator so that the two workers can jointly lift the burden and carry it to the point of delivery with a manual hand truck. Thus, it is common for package delivery businesses impose two weight limits on packages accepted for delivery. If a package weighs less than a first weight limit (commonly fifty to seventy pounds), it is delivered by a single operator. If the package weighs more than the first weight limit but less than the second (which may be set at one and one half to two times the first weight limit), it is delivered by an operator and an assistant. If the package exceeds the second weight limit, it is deemed to be too large to handle by conventional package delivery means and must be handled by other means, such as delivering it on a medium or heavy duty truck to a loading dock.
Even though package delivery business set weight limits on packages handled, on-the-job lifting injuries are unpleasantly common. Many of these injuries, as well as the operating expense of sending an assistant along whenever a single somewhat heavy package needed to be delivered, could be avoided by providing a hand truck that was light enough to be conveniently used with relatively small packages, but that provided a power assist to allow a single operator to handle somewhat heavy articles. Clearly, neither the hand truck, nor the power assist unit, nor any other separately handled portion of the hand trucking apparatus should exceed the weight limit for single operator handling.
There are several prior art hand trucks that include power means, primarily for urging the hand truck up stairs or the like. Such hand trucks most often take one of two forms: 1) a hand truck having a track that may be relatively wide so as to extend across much of the width of a stair tread and that may include a plurality of cleats thereon, the cleats engaging the edges of steps to move the hand truck up or down the steps (such as that shown in U.S. Pat. No. 3,092,200); and, 2) a hand truck having a continuous belt including at least one relatively narrow protruding member for engaging steps (such as that shown in U.S. Pat. No. 3,330,370), where the protruding member is long enough to extend well past the lip of a stair tread. It is noted that the prior art does not depict powered means adapted to engage a large percentage of a stair tread by extending relatively far across both the width and the depth of a stair tread.
The prior art powered hand trucks are usually very heavy, complex and unwieldy to use. Additionally, one of the difficulties in handling freight is in moving the freight from a truck to the ground, and the prior art hand trucks have no provisions for assisting such motion. The conventional equipment for unloading a truck is a fork lift, but this is a very heavy and expensive piece of industrial equipment that is not economical for use in consumer oriented freight.
Thus, the prior art has not provided a convenient piece of equipment for handling freight and the like for moving the freight from a truck to a consumer.